Effects of Straw Interlayer Combined with Spring Irrigation on Saline- Alkali Soil Respiration and Its Temperature Sensitivity in Hetao Irrigation District

This study was conducted to explore the responses of saline-alkali soil respiration to straw interlayer and irrigation regime, and to clarify the relationships between soil respiration rate and soil temperature/water content in Hetao Irrigation District.

A randomized block design was set up in 2015 with three treatments: autumn and spring irrigation (I_SA), spring irrigation without autumn irrigation (I_S), and spring irrigation plus straw interlayer without autumn irrigation (SI_S). Soil respiration, soil temperature and moisture content were measured in 2017 and 2018, and the temperature sensitivity of soil respiration rate was also estimated.

(1) Soil temperature and soil moisture content in the 0-20 cm soil layer fluctuated obviously, while it was relatively stable in the 20-40 cm soil layer. SI_S increased the soil temperature in 0-40 cm soil depth and moisture content in 20-40 cm soil depth. (2) The soil respiration rate in 2017 was higher than that in 2018. It was the highest in the flowering stage, followed by budding stage, before spring irrigation, before sowing, and harvest stage. (3) The soil respiration rates of I_S and SI_S were significantly higher than I_SA at the flowering stage (P<0.05). Compared with I_SA, I_S and SI_S increased soil respiration rate by 0.12-0.44 and 0.06-0.42 μmol·m^-2·s^-1, respectively. Compared with the I_S, the soil respiration rate of SI_S decreased by 0.01-0.49 μmol·m^-2·s^-1. These results indicated that the soil respiration rate was increased without autumn irrigation, while it was decreased with straw interlayer. (4) The soil respiration rate positively correlated with soil temperature (P<0.01), while it had no significant correlation with soil moisture content. Soil temperature at the 0-20 and 20-40 cm soil layer explained 40.74%-53.84% and 39.27%-53.46% variation of soil respiration rate, respectively. (5) The temperature sensitivity of soil respiration (Q₁₀) varied within 1.68-1.98 for different treatments, and the Q₁₀ of the 20-40 cm soil depth was higher than that of the 0-20 cm soil depth. Compared with I_SA, I_S and SI_S reduced Q₁₀. However, SI_S increased Q₁₀ compared with I_S.

Overall, the straw interlayer increased the soil temperature in 0-40 cm soil depth and moisture content in 20-40 cm soil depth, reduced soil respiration rate, and increased the temperature sensitivity of soil respiration, which was used as an effective practice for water saving and emission reduction in the Hetao Irrigation District.